Roadside Revegetation

PLANNING PHASE TWO: ASSESS SITE
Relative Moisture
High
Low
Soil Moisture
A
ET
PMS
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Months
Figure 5-22 | Relationships among
evapotranspiration, soil moisture,and
plant moisture stress
Conceptual relationship between evapotranspiration
(ET), soil moisture, and plant moisture stress (PMS).
In the western United State, PMS lags behind ET in
late spring because soil moisture is still moderate to
high from the winter rains. By mid summer (A), plant
moisture stress has increased to its greatest level in
the year because soil moisture is at its lowest. Newly
planted seedlings undergo extreme stress during this
period. Unless the seedlings are dormant or their root
systems have grown deeper into the soil, where there
is greater access to soil moisture, seedlings will die. In
late summer and early fall, cooler weather returns and
rains wet the soil, driving ET and PMS rates down again.
D
E
F
Figure 5-23 | Plant moisture stress
Plant moisture stress (PMS) is a measure of the tension
or pull of moisture through a vascular plant. Much like a
straw, when the demand for moisture at the surface of
leaves is high, moisture is drawn from the stomata. This
creates a pull of water through the leaves, stem, and
down to the roots, which draws water from the soil.
C
A
B
Location Water Potential
(MPa)
Soil (A)
- 0.1
Plant Roots (B) - 0.3
Plant Stem (C) - 0.6
Plant Leaf (D) - 0.9
Plant Stomata (E) - 25.0
Atmosphere (F) - 125.0
5.4.1 WIND
Wind is often overlooked as a factor in the success or failure of establishing native vegetation,
but it can play a major role, especially on sites where summers are hot and dry and soil
moisture levels are low. Until seedlings become established, wind can place extremely high
demands for moisture on newly planted seedlings, severely limit growth, and ultimately lead
to death. Wind can also be an important factor for surface stability, as discussed in Section
5.6, Surface Stability.
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
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